Migration of Immune Cells

How do immune cells travel in the body when there is no infection they have to fight? Scientists of a national research laboratory in the northeast of Berlin (Germany), have identified a molecule which directs the migration of immune cells through the body into specific lymphoid organs where they receive training for their future tasks. The work of Reinhold Förster, Anita Mattis and Martin Lipp from the Max Delbrück Center for Molecular Medicine (MDC) in Berlin-Buch and their co-workers Elisabeth Kremmer (GSF Research Center, Munich) and Eckhard Wolf and Gottfried Brem (Gene Center, University of Munich) has now been published in the American journal Cell (Vol.87, No. 6, pp. 1037 – 1047, 13 December 1996).

A specific form of immune cells, called lymphocytes, plays a crucial role in the body´s fight against pathogens. Lymphocytes — B‑and T‑cells — have the remarkable capacity of developing a memory. Thus they are able to detect a known pathogen much faster and enable its destruction. This way these memory cells of the immune system protect the body from being infected a second time, as for instance with measles. This is also the principle on which vaccination is based.

But before lymphocytes are able to recognize a pathogen, they must be trained. This happens in specific anatomic compartments of the spleen and of the lymph nodes, called germinal centres. In these germinal centres B cells for example receive not only special training which allows them to produce highly active antibodies to fight pathogens — but also to develop an ​„immunological memory“.

Scientists have been speculating for quite some time, that special signalling substances, called chemokines, help T and B cells to find their way into the germinal centres of lymphoid organs like lymph nodes and spleen. Chemokines are substances produced by body cells which direct other cells in a certain direction to reach a specific goal. Chemokines bind to certain chemokine receptor molecules in the membrane of cells.

The MDC research group of Martin Lipp were the first to detect a chemokine receptor, called BLR1, on mature B cells and memory T cells some time ago. This receptor is highly related to the recently detected HIV coreceptor which is also a member of the chemokine receptor family. Now, Martin Lipp, Reinhold Förster and Anita Mattis also succeeded in detecting the function of the BLR1 receptor. They found, that the spleen of mice that lacked this specific receptor, was functionally impaired: no germinal centres had been formed. Martin Lipp and his group were also able to show for the first time that, although activated B cells did get into the spleen, they were not able to enter the so-called B cell zone to form germinal centres. The impaired migration process of these lymphocytes also resulted in the total absence of specific tissue of the immune system in the small intestine, so-called Peyer´s patches. Now Martin Lipp and his colleagues are trying to find out, what role the BLR1 receptor plays in the development of infectious diseases and metastasis of tumours.

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